The present invention relates to a coffee-making device, comprising a coffee supply line, a hot water supply line with a pump, a beverage outlet with shut-off valve, and a coffee outlet, said coffee-making device comprises a brewing compartment for holding coffee, which brewing compartment is connected to said water supply line and to said beverage outlet, said brewing compartment comprising a cylinder in which a piston is capable of reciprocating.
Such a device is known from EP 0380450A2, which discloses a structure in which various types of coffee can be conveyed separately from various containers into the brewing compartment.
Ordinary coffee and espresso coffee have their own specific characteristics in the brewing process, such as, for example, the brewing quantity, the type of coffee, the water temperature, the contact time between coffee and water, and the pressure in the coffee bed.
If there is a desire for several brewing processes to be achieved in one brewing system, the type of coffee and the water temperature are easy to change for this.
It is much more difficult to switch over the pressure and the brewing quantity desired at this pressure.
It is the object of the present invention to provide a single brewing system by means of which it is possible to carry out different brewing processes. This object is achieved in a coffee-making device of the type described above in that said shut-off valve is designed to provide either a first passage with relatively small surface or a second passage with relatively large surface, and wherein said pump is designed to provide for an appropriate first, small volume displacement at high pressure and a second, large volume displacement at low pressure.
According to the invention, it is possible to prepare different types of coffee with a single coffee-making device by, apart from varying the sort and quantity of coffee, varying the throughput pressure of the water. The latter is controlled by the shut-off valve, which can provide for various passages, and thus can regulate the pressure in the brewing system. All the above is, of course, also dependent upon the pump. The term shut-off valve can be understood to mean one or more electrically operated shut-off valves.
According to an advantageous embodiment of the invention, the shut-off valve is, however, operated by the pressure of the water displaced by the pump. To this end, the shut-off valve comprises a restriction which reacts to pressure and is designed in such a way that at relatively low pressure a restriction with larger passage is present and at relatively higher pressure a restriction with smaller passage is present.
The valve structure is designed in such a way that at relatively low pressure a relatively large passage is present. When the pressure increases, the passage will become smaller.
In this way it is possible, without further mechanical components and/or controls, to build up a higher pressure in the brewing chamber depending on the pressure of the water that is moving through the coffee. In this way, the pressure in the brewing chamber can be varied simply by being controlled by the inlet pressure of the water. This makes it possible in a simple manner to prepare either xe2x80x9cordinaryxe2x80x9d coffee or espresso coffee, or variants of these.
It will be understood that the valve structure just described can also be used in combination with other coffee-making devices known in the prior art. After all, this valve structure is entirely independent of the remainder of the coffee-making devices. Of course, the fact is that the already simple structure of the coffee-making device is further simplified by using such a valve.
According to an advantageous embodiment of the invention, such a structure is used in the case of a coffee-making device comprising a cylinder with piston movable therein. In this case the water supply is connected to the volume present above said cylinder, and means for containing coffee are present near the free end of said cylinder. The term xe2x80x9cabovexe2x80x9d in this description indicates the position away from the drive end.
According to a further advantageous embodiment of the invention, the piston comprises a piston head provided with a seal acting relative to said cylinder, an inlet channel being provided in said piston below said piston head, which inlet channel is sealed off relative to said cylinder and can be connected to said water supply in at least two different positions of said piston relative to said cylinder.
According to another advantageous embodiment, the channel is connected by way of a non-return valve to the compartment above the cylinder.
In order to ensure that the piston functions even in the case of varying amounts of coffee and also that the coffee-making device is of a simple design, according to an advantageous embodiment, provision is made for a coffee-making device comprising a housing with a cylinder in which a piston is provided, for compressing with the piston coffee placed on said piston, said piston being movable by means of a drive mechanism, and said drive mechanism being provided in said housing, and comprising a cover that can be placed on said cylinder, in order to bound a compression chamber with said cylinder and piston, means for introducing water into the compression chamber, means for discharging brewed coffee from the compression chamber, and also means for removing the compressed coffee tablet, said movable cover comprising a swivelling arm structure which is rotatable around an axis substantially perpendicular to the axis of said cylinder in such a way that said cover can be moved above and away from the end of the cylinder, which swivelling arm structure is capable of reciprocating substantially perpendicular to the axis of rotation thereof, in order to bring said cover into engagement in a sealing manner with said cylinder end, said drive mechanism being designed to operate both said piston and said swivelling arm, and comprising a rotary input shaft, and in which said drive mechanism for said piston is provided with means for converting a uniform rotating motion into a non-uniform reciprocating motion.
The closing and opening characteristic of the piston in the cylinder unit can be influenced, in other words optimized, by converting the uniform linear rotating motion of the drive motor in some way into a non-linear motion.
Such a non-linear motion characteristic of the piston can be obtained in any way known in the prior art. An example that can be mentioned is a curved disc which is driven by the rotary motor and in turn drives the piston. A certain opening and closing characteristic of the piston can be obtained through the special shape of the curve.
Another possibility is to use a crankshaft structure.
In this way a particularly compact structure can be obtained with a single drive motor. More particularly, the actual coffee-making process can be carried out irrespective of the xe2x80x9ctablet thicknessxe2x80x9d of the coffee material. This means that it is possible to vary the quantity of coffee material without this affecting the functioning of the device, in other words various types of coffee can be made with one device without special measures as regards structure being necessary.
A particularly simple structure can be obtained by using a swivelling arm structure for moving the cover on the cylinder. Owing to the fact that the swivelling arm rotates substantially about the axis of the crankshaft, a particularly compact device is obtained.
Such a swivelling arm structure can be driven in any way known in the prior art. However, it is preferably driven by the crankshaft. If the structure is designed in a suitable manner, it is possible for it to be driven directly by the crankshaft, in other words without interposing gearwheels and other transmission mechanisms.
The reciprocating motion of the rocker arm in order to place the cover on the fee end of the cylinder in a sealing manner can also be carried out in any way known in the prior art. It is, however, preferably embodied by means of a cam/cam follower mechanism. This cam/cam follower mechanism is preferably likewise fitted on the crankshaft of the piston. By this measure also, further simplification of the coffee-making device according to the invention can be obtained. The coffee-making device can consequently be manufactured more cheaply, and fewer components will wear, and any parts that may have worn will be easier to replace. Cleaning can also be carried out in a simple manner.
The structure described above works in particular if the crankshaft rotates in different directions, in other words. It does not rotate in only one direction during a coffee-making operation. In particular, if a combination with cams/cam followers is envisaged for driving the swivelling arm structure, such a motion in different directions is advantageous. Of course, a corresponding, suitable control is present.
Certain parts of the motion process of the swivelling arm structure can be controlled by means of a spring or the like.
Of course, it is the case that the already simple structure of the coffee-making device is further simplified by using such a valve.